This invention relates to snap-fittings and particularly to snap-fit polymeric journal bearings used, for example, in photographic film processors. The invention concerns the design structure, manufacture, and use of such articles.
A major problem with respect to the use of polymeric journal bearings in photographic film processors has been the relatively high wear rates associated with their use. This is particularly true of low molecular weight injection-molded polymeric bearings. Such bearings have relatively short lives when subjected to corrosive fluids and/or abrasive environments containing dirt and other foreign particulate matter.
High and ultrahigh molecular weight (molecular weight greater than 1,000,000) polymeric bearings exhibit a greatly improved wear rate over those of lower molecular weight. However, the cost of bearings prepared from higher molecular weight polymeric materials has not been competitive with that of low molecular weight polymeric bearings. Unlike low molecular weight polymeric materials, high and ultrahigh molecular weight polymeric materials are not feasibly injection-molded. The greater the molecular weight, the more difficult injection molding becomes. Hence, the higher molecular weight materials must be machined at resultingly greater costs. Thus, there has been a need for high and ultrahigh molecular weight polymeric bearings, which can be provided at a cost comparing more favorably with injection-molded low density polymeric bearings.